Centrifugal compressors are employed in a wide variety of applications where it is desired to increase the pressure of a fluid. One particularly important application is in the industrial gas industry wherein centrifugal compressors are employed to pressurize feed air prior to cryogenic rectification into product industrial gases, or to pressurize industrial gases prior to liquefication.
A centrifugal compressor is comprised of a rotatable centrally oriented shaft, an impeller wheel mounted on the shaft, a diffuser leading radially outward from the impeller wheel to a volute, and an exit communicating with the volute. Gas flows into the centrifugal compressor and flows between curved blades mounted on the impeller wheel. The rotating shaft-wheel assembly imparts a velocity to the fluid. The velocity is converted to pressure energy as the gas passes sequentially through the diffuser, volute, and exit.
Centrifugal compressors consume very large amounts of power, such as electrical power. In some applications, such as in the cryogenic rectification of air wherein the pressure of the feed air constitutes essentially all of the energy input to the process, the energy consumed by a centrifugal compressor is a major cost consideration and even a small improvement in centrifugal compressor efficiency will have a significant positive impact on the economics of the process. Centrifugal compressor efficiency may be defined as the measure of the energy required to raise the pressure of a given fluid from a first to a second pressure.
Accordingly it is an object of this invention to provide a centrifugal compressor for increasing the pressure of a fluid at greater efficiency than heretofore available centrifugal compressors.